During the next year we intend to: (a) complete our restriction mapping studies on the HPO and tumor tissues, and (b) complete our restriction mapping of the Bgl II restriction fragment from the GR strain of MMTV. We will use the restriction map of this GR-Bgl II fragment as a basis for studying the analogous region of the integrated genomes of different MMTV strains. In addition, we intend to (c) initiate experiments leading to the determination of the sequence of the 3'-end of the MMTV genome.